Athletic mouthguard



FIG. 1 is a front perspective view of an athletic mouthguard, showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a left side view thereof; and,

FIG. 7 is a right side view thereof.

The dashed lines shown in the figures are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for an athletic mouthguard, as shown and described. 